It is known that a sodium-dependent glucose transporter, herein after referred to as “SGLT”, which is a co-transporter of monosaccharide and sodium has some subtypes. Namely, a sodium-dependent glucose transporter 1, herein after referred to as “SGLT1”, exists mainly in the small intestine and the S3 segment of the kidney's proximal tubule, and a sodium-dependent glucose transporter 2, herein after referred to as “SGLT2”, exists mainly in the S1 segment of the kidney's proximal tubule.
Among them, SGLT1 which exists in the small intestine participates in glucose and galactose absorption from the digestive tract (Non-patent references 1 and 2). In diabetic patients, carbohydrate digestion and absorption increase. Actually, it is confirmed that SGLT1 and its mRNA highly increase in the small intestine (see Non-patent reference 3). Therefore, inhibiting SGLT1 can control increase of blood sugar level by suppression of glucose and galactose absorption in the small intestine (see Patent reference 1).
On the other hand, SGLT2 participates in reabsorption of glucose filtrated through the glomerulus (see Non-patent reference 4). Therefore, inhibiting SGLT2 can normalize blood sugar level by suppression of glucose reabsorption (see Patent reference 5).
As compounds inhibiting SGLT1, pyrazole derivatives (see Patent references 1 and 2), benzylphenol derivatives (see Patent reference 3) and the like are known. And as compounds inhibiting SGLT2, glucopyranosyloxypyrazole derivatives (see Patent reference 4), glucopyranosyloxybenzylbenzene derivatives (see Patent reference 5) and the like are known. Both of the above-mentioned SGLT1 inhibitors and SGLT2 inhibitors are O-glucoside derivatives wherein a glucopyranosyl group binds to an aryl group or a heteroaryl group through an oxygen atom.
Recently, it was reported that regarding fluoroglycoside heterocyclic derivatives (see Patent reference 6) and C-glucoside derivatives whose glucopyranosyl group binds to a carbon atom in a ring of a nitrogen-containing heterocyclic compound (see Patent reference 7), they show an SGLT inhibitory activity. However, in these reports, nothing was described or suggested concerning a compound which has a substituent such as an aryl group on a nitrogen atom at 1-position of a fused cyclic nitrogen-containing heterocyclic compound and a glycopyranosyl group such as a glycopuranosyl group, a galactopyranosyl group or the like at 3-position of the same.    [Non-patent reference 1] Yoshikatsu Kanai, Kidney and Dialysis, 1998.12, Vol. 45, extra edition, pp. 232-237;    [Non-patent reference 2] E. Turk and 4 persons, Nature, 1991.3, Vol. 350, pp. 354-356;    [Non-patent reference 3] J. Dyer and 4 persons, American Journal of Physiology, 2002.2, Vol. 282, No. 2, pp. G241-G248;    [Non-patent reference 4] Yoshikatsu Kanai and 4 persons, J. Clin. Invest., 1994.1, Vol. 93, pp. 397-404;    [Patent reference 1] International Publication No. WO04/014932 pamphlet;    [Patent reference 2] International Publication No. WO04/018491 pamphlet;    [Patent reference 3] Japanese patent publication No. JP2004-196788;    [Patent reference 4] International publication No. WO01/16147 pamphlet;    [Patent reference 5] International publication No. WO01/68660 pamphlet;    [Patent reference 6] International publication No. WO04/052903 pamphlet;    [Patent reference 7] International publication No. WO04/080990 pamphlet.